This invention relates to an apparatus in the field of spinning preparation and is more particularly concerned with determining the quantities of fiber such as cotton, chemical fibers or the like pneumatically conveyed through a duct with flow rate control. The apparatus includes a sensor unit which monitors the advancing fiber stream.
In fiber processing machines which serve for the spinning preparation of fiber, the momentary fiber quantity actually being conveyed has to be determined particularly in case the rate of fiber feed is to be regulated. In order to be able, for example, to adapt the feed of a bale opener to the fiber material requirement of the subsequent fiber processing machines of a fiber processing line, it has to be determined how much fiber material the bale opener produces at any given moment.
A known apparatus comprises an optical barrier assembly which functions as a sensor for setting the fiber removal height of the detaching device of a bale opener. The optical barrier assembly is formed of a light emitter and a photocell (such as a selenium cell) responding to the incident light. The emitter and receiver are connected by means of control conductors with a switching device, for example, a switching relay station. The optical barrier assembly is mounted on the outlet duct for the fiber detached from the fiber bales. It is feasible to provide a plurality of light emitters and light detectors, whose switching relays are each set to a predetermined density of the fiber stream. In such an arrangement where a predetermined switching relay is set to respond to a predetermined quantity throughput, there is effected, by means of the relay, an upward or downward motion of the fiber detaching device (for example, one or more sawtooth rollers), together with the housing in which the detaching device is accommodated. In this manner there is ensured a constant fiber flow rate during the fiber bale opening process. If an optical barrier device is used which has a single light emitter and a single detector, all that can be determined is whether or not fiber material passes between the emitter and the receiver. The actual quantity of the fiber material throughput thus cannot be ascertained. In case a plurality of emitters and receivers is used with the associated separate switching relays, a determination of the actual throughput quantity is also not possible, because at each time only stepwise one or the other emitter/receiver pair is connected to the associated relay. Since a constant fiber stream is being produced, a regulation as a function of a variable fiber stream, particularly as a function of the quantity requirements by the after-connected fiber processing machines is not possible with prior art arrangements discussed above.